Exposure method and exposure apparatus

ABSTRACT

A pattern enlarged from a transfer pattern is divided into patterns (Pi) of a plurality of master reticles (Ri). Images of the patterns (Pi) of the plurality of master reticles (Ri) reduced by a projection optical system are successively-projected and exposed on the surface of a blank (mask substrate) while stitching. Marks (M 1 , M 2 ) indicating identification information for identifying a master reticle from another master reticle, transfer positions, etc. are formed on the master reticles (Ri). These marks (M 1 , M 2 ) are detected before the exposure and exposure is performed in accordance with the information on the transfer position etc. shown by the marks (M 1 , M 2 ) or reticle information (exposure conditions, various correction values, etc.) relating to the master reticles stored and held in advance corresponding to the identification information. The number of work steps when producing a working reticle using the plurality of master reticles is reduced and occurrence of work errors can be prevented.

TECHNICAL FIELD

The present invention relates to an exposure method used when producinga photomask used for producing a semiconductor integrated circuit, aliquid crystal display device, a thin film magnetic head, or anothermicrodevice by photolithography and an exposure apparatus for workingthe exposure method.

BACKGROUND ART

In photolithography process of a semiconductor device, a pattern of aphotomask is transferred on to a wafer or glass plate coated with aphotoresist (hereinafter also called a “photosensitive substrate”). Asthis type of projection exposure apparatus, wide use has been used inthe past of a step-and-repeat type exposure apparatus (stepper). Thisstep-and-repeat type exposure apparatus exposes and transfers a patternof a photomask by reduction projection on individual shot areas of thewafer. Therefore, when exposure of one shot area ends, the wafer ismoved for exposure of the next shot area. This process is successivelyrepeated.

Further, to increase the range of exposure of the mask pattern, astep-and-scan type exposure apparatus (scanning stepper) has beendeveloped which synchronously moves the mask and wafer in scanningmotion with the projection optical system in a state of restricting theexposure light from the illumination system into a slit shape (forexample, rectangular shape) and projecting reduction image of a part ofa mask pattern using the slit light. This step-and-scan type exposureapparatus (scanning stepper) has the advantages of an aligner transfermethod of transferring the pattern of the entire surface of the mask tothe entire surface of the wafer at an equal magnification by a singlescan exposure and the advantages of the stepper transfer method. Notethat a photomask used in a step-and-repeat type or step-and-scan typereduction projection type exposure apparatus is also called a “reticle”.

The photomask used in such an exposure apparatus has conventionally beenproduced by drawing a master pattern on a photomask substrate using anelectron beam lithography system or a laser beam lithography, system.That is, a mask material is formed on the substrate, a resist is coatedon it, then the master pattern is drawn using an electron beamlithography system or laser beam lithography system. Next, the resist isdeveloped and etched etc. to form the master pattern by the maskmaterial. In this case, if the magnification rate of the reductionprojection type exposure apparatus using this photomask is 1/β, themaster pattern drawn on the photomask may be the pattern of the deviceenlarged β-fold, therefore the drawing error due to the lithographysystem is reduced to about 1/β on the device. Therefore, it becomespossible to form the pattern of the device by a resolving power of about1/β of the resolving power of the lithography system.

As explained above, in the past, the master pattern-of the photomask hasbeen drawn by an electron beam lithography system or laser beamlithography system. These lithography systems draw master patternsdirectly based on the drawing data from a control computer. Recent LSIsand other devices, however, have become larger in size and improved infineness and integration, so the master pattern of the photomaskrequired for exposure also becomes larger in area and finer. Further, asthe photomask, use is also made of a reticle for double exposureprovided with a correction pattern for preventing transfer ofunnecessary patterns, a so-called phase shift reticle provided with aphase shifter between adjoining patterns, etc. With these specialphotomasks, however, the amount of the drawing data tends to becomegreater than that of other photomasks. Due to this, the amount ofdrawing data required in an exposure apparatus for producing a photomaskbecomes massive.

Therefore, the drawing time required for drawing a master pattern of aphotomask by such a lithography system has recently grown from 10 hoursto around 24 hours. This increase in the drawing time is becoming afactor behind the rising cost of manufacture of a photomask.

In this regard, in an electron beam lithography system, it is necessaryto correct the proximity effect caused by the back scatteringdistinctive to an electron beam. Further, it is necessary to correct theuneven electric field around the substrate due to the charging of thesurface of the substrate. Therefore, to draw a master pattern asdesigned, it is necessary to measure the error of the drawing positionetc. in advance under various conditions and make complicatedcorrections at a high accuracy and stability at the time of drawing.Making such complicated corrections during an extremely long drawingtime such as the above with a high accuracy and stability on acontinuous basis, however, is difficult. The disadvantage arises ofdrift of the drawing position during the drawing. Further, it ispossible to suspend the drawing for calibration, but this has thedisadvantage of the overall drawing time becoming even longer.

Further, the resolving power and other characteristics of the resist forelectron beam use have not been improved that much. No rapid improvementin these characteristics is expected in the future as well. Therefore,if the pattern rule of semiconductor devices becomes finer in thefuture, the drawing time for the master pattern of a photomask is liableto become too long and the resolving power of the electron beam resistis liable to approach its limit making the required drawing accuracyimpossible to obtain. Further, the amount of the drawing data in thecontrol computer is also becoming massive to-the extent of difficultyfor use in a single drawing operation.

A laser beam lithography system draws a master pattern using anultraviolet band laser beam. There are the advantages that it ispossible to use a resist giving a higher resolving power compared withan electron beam lithography system and that there is no proximityeffect due to back scattering. The resolving power of a laser beamlithography system is inferior to that of an electron beam lithographysystem, however. Further, in a laser beam lithography system, since amaster pattern is drawn directly in this system, the amount of drawingdata becomes massive and data processing becomes difficult. Further, thedrawing time becomes extremely long. Therefore, the required drawingaccuracy is liable to not be able to be obtained due to drift of thedrawing position etc.

To solve the above problem, the present assignee previously proposed anapparatus which enlarges the pattern for transfer, divides the patterninto a plurality of patterns of master masks, and successively projectsand exposes images of the plurality of patterns of the mask patternsreduced by the projection optical system on the surface of the masksubstrate (blank) while stitching them (hereinafter sometimes called a“reticle exposure apparatus” or a “mask exposure apparatus”).

When producing a photomask used for the production of a microdevice(working mask) using a reticle exposure apparatus, a thin film of a maskmaterial is formed on a mask substrate as the photomask substrate and aresist or other photosensitive material is coated on it. Next, reducedimages of the plurality of patterns of master masks are transferred tothe photosensitive material for example by an optical type reductionprojection exposure apparatus by the step-and-repeat system or thestep-and-scan system. By etching using the pattern of the remainingphotosensitive material as a mask, a desired pattern for transfer(master pattern) is formed.

At this time, if the magnification rate of a for example optical typeexposure apparatus for producing a photomask is made 1/α (where a is aninteger or fraction etc. larger than 1), the transfer pattern, that is,the master pattern, is enlarged α-fold. This enlarged master pattern isdivided into for example a x α number of patterns of master masks. Ifthe magnification rate is 1/5 (α=5), 5×5=25 master masks are provided.As a result, since the patterns formed on the master masks are parts ofthe master pattern enlarged α-fold from the master pattern, the amountsof the drawing data of the patterns of the master masks are reduced toabout 1/α² of the past and the minimum line widths become α-times thepast. Therefore, the patterns of the master masks can be drawn in ashort time with little drift and with a high accuracy using for examplea conventional electron beam lithography system or laser beamlithography system. For example, since the drawing error of thelithography system is reduced to 1/α on the photomask, the accuracy ofthe master pattern is further improved. Further, once these master masksare produced, the patterns of these master masks can be transferred at ahigh speed on to the substrate of the photomask by the step-and-repeatsystem etc., so the production time when producing a plurality ofphotomasks can be greatly reduced compared with the method of drawingindividually by the lithography systems.

When there is an error in part of the patterns of the master masks atthe time of formation or a change occurs in part of the master patternafter production, it is sufficient to correct or remake only the mastermasks including the part with the error or the master masks includingthe changed part. Since there is no effect on the plurality of mastermasks as a whole, it is possible to deal with these cases at a highefficiency.

When producing a working mask using a plurality of master masks,however, the plant producing the working mask stores a large number ofmaster masks for dealing with all of the working masks to be produced.Therefore, when producing a working mask, the operator (worker) etc. hasto set a plurality of master masks used in the production process (maskexposure apparatus) taking into consideration conditions such as at whatposition on the mask substrate (blank) of what layer of what product isbeing exposed. This work is extremely complicated resulting in easyoccurrence of work errors.

Further, the various exposure conditions (exposure time, focus position,blind size, illumination conditions, shot XY magnification, etc.) differfor each master mask, so it is necessary to input and designate therespective exposure conditions or, when correcting the various error,input and designate the correction information for the same (correctionvalues for deformation accompanying support of master mask, distortionof projection exposure apparatus, coma aberration, or other aberration,and deformation accompanying support of mask substrate etc.) The aboveproblem was therefore extremely serious.

DISCLOSURE OF THE INVENTION

Therefore, an object of the present invention is to reduce the number ofwork steps and prevent the occurrence of work error when producing aphotomask using a plurality of master masks.

Further, another object of the present invention is to produce a highaccuracy photomask.

Note that in the following explanation, the present invention will beexplained with reference to the reference numerals of members shown inthe figures showing the embodiments, but the requirements of the presentinvention are not limited to the members given reference numerals andshown in the figure.

1. According to one aspect of the present invention, there is provided amethod of dividing a pattern enlarged from a transfer pattern (27) intoa plurality of patterns of master masks (Ri) and successively projectingand exposing images of the plurality of patterns (Pi) of master masksreduced by a projection optical system (3) on the surface of the masksubstrate while stitching them, the method of exposure comprising stepsof forming marks (M1, M2) including identification information foridentifying one master mask from another master mask on each of themaster masks, storing in advance mask information relating to the mastermasks corresponding to the identification information, detecting themark of the master mask before exposure, and performing exposure inaccordance with mask information corresponding to the identificationinformation shown by the mark.

The master mask is formed with the mark including identificationinformation for identifying the master mask from another master mask.The mark is detected before exposure and exposure is performed inaccordance with mask information corresponding to the identificationinformation shown by the mark, so by setting positional informationshowing the position on the mask substrate where the pattern of themaster mask is to be transferred as the mask information, the operatoretc. can simply extract the plurality of master masks required forproduction of a photomask and set them freely without identifying themin order to have the image of the pattern of the master mask transferredto the corresponding position on the mask substrate. Therefore, theoperator etc. no longer has to set the masks considering conditionsrelating to the position such as for which position on the masksubstrate the master mask is to be used for exposure, so the workbecomes extremely easy and work errors become less frequent.

The mask information includes, in addition to the positional informationshowing the position on the mask substrate where the pattern of themaster mask is to be transferred, for example correction information forcanceling out deformation accompanying support of the master mask,aberration of the projection optical system, and deformationaccompanying support of the mask substrate, the exposure time for themaster mask, focus position, blind size, illumination conditions, shotmagnification, and other exposure conditions, etc. Part or all of thesemay be included. By storing these correction information, exposureconditions, etc., intervention of an operator for the correctioninformation or exposure conditions is no longer necessary, the number ofwork steps can be reduced, and input errors etc. are prevented. Further,even if the operator mistakenly sets different types of master masks, itis possible to identify this, so measures such as warnings can bedevised and it is possible to eliminate the problem of exposure usingmaster masks having no relation to the production of a working mask.

As the mark, it is possible to use a bar code mark or a spatial imagemeasurement mark. When using a spatial image measurement mark, it ispossible to use the mark for alignment of the master mask or correctvarious error based on the results of spatial image measurement. Themark may be detected in the state with the master mask held on the maskstage.

The above method forms a mark as identification information on themaster mask. Corresponding mask information is stored in a storagedevice etc. This is particularly effective when there is a large amountof mask information. When the mask information is not that large, it ispossible to directly form the mark including the mask information on themaster mask. That is, it is possible to provide a method of dividing apattern enlarged from a transfer pattern into a plurality of patterns ofmaster masks and successively project and expose images of the pluralityof patterns of master masks reduced by a projection optical system on tothe surface of a mask substrate while stitching them where marksincluding mask information relating to the master masks are formed oneach of the master masks and exposure is performed in accordance withthe mask information shown by the marks.

An exposure apparatus of the present invention for working the abovemethod of exposure provided with a plurality of master masks (Ri) formedwith marks (M1) including positional information indicating a transferposition on a mask substrate (4) to be processed, a mask magazine (16)for storing the plurality of master masks, a mask stage (2) on which onemaster mask selected from the mask magazine is placed, a projectionoptical system (3) for projecting a reduced image of a pattern of themaster mask on the mask stage on to a mask substrate, a substrate stage(6) for positioning the mask substrate on a plane vertical to an opticalaxis of the projection optical system, a detection device (56) fordetecting content of the mark of the master mask on the mask stage, anda control device (9) for exposure in accordance with positionalinformation shown by the mark detected by the detection device.

According to the exposure apparatus of the present invention, by formingthe master mask with the mark including positional information showingthe transfer position on the mask substrate where the pattern of themaster mask is to be transferred, detecting the mark on the mask stage,and performing exposure at a position in accordance with the positionalinformation shown by the mark, the operator etc. need only randomly loadthe plurality of master masks required for production of a photomask inthe mask magazine in order to get the images of the patterns of themaster masks transferred to the corresponding positions on the masksubstrate. Therefore, the operator etc. no longer has to set the masksconsidering conditions relating to position such as for which positionson the mask substrate the master masks are to be used for exposure, sothe work becomes extremely easy and work errors become less frequent.

2. According to another aspect of the present invention, there isprovided a method of exposure for irradiating exposure light on aplurality of master masks (Ri) formed by dividing an enlarged pattern ofa transfer pattern (27), reducing a pattern image of the same for eachmaster mask, and transferring the same on to a mask substrate (4) onwhich the transfer pattern is to be formed, the method of exposurecomprising steps of detecting deformation information (dxi, dyi) of themask substrate corresponding to a transfer position of a pattern imageand adjusting at least one of the relative positional relationshipbetween the pattern image and the mask substrate at the time of transferof the pattern image and the projection characteristics of the patternimage based on the deformation information. In this case, an exposureamount of said mask substrate can be changed in accordance with a changeamount of a line width of the pattern image for every said master mask.Note that in the description and claims of the present application,“detecting deformation information” includes finding deformationinformation by actual measurement or finding it by simulation(calculation).

When successively projecting and exposing patterns while stitching them,since the positional accuracy or shape accuracy of the connecting partsof the patterns transferred by the master masks has a major effect onthe quality or reliability of the photomask which is produced, it isextremely important that the positional or shape accuracy of the patternbe high. The mask substrate to be exposed is supported by apredetermined supporting method at the time of exposure, but flexingoccurs due to the substrate's own weight in accordance with the supportmethod. This flexing differs depending on the position (shot) on themask substrate, so sometimes the pattern distorts, misalignment occursat the stitched parts of the patterns, or other cases occur not allowingtransfer of patterns with a high accuracy.

Therefore, the method of exposure of the present invention detectsdeformation information of the mask substrate and adjusts (deforms) theshape of a pattern image to be transferred in accordance with theflexing or other deformation of the mask substrate for transfer. Thatis, the shape of the projected image on the surface is adjusted to thedesired shape in the state with the mask substrate deformed in this way.Due to this, it is possible to produce a high quality, high reliabilityphotomask. As the deformation information, for example, it is possibleto employ as a standard the information in the case of supporting themask substrate theoretically flat. By making adjustment based on thisdeformation information, it is possible to form a pattern having apattern shape close to the ideal pattern shape in the state with thephotomask produced supported ideally flat. The deformation information,however, is not limited to the standard of the ideal shape. It is alsopossible to use deformation information based on the state supported onthe mask stage etc. of the device exposure apparatus (exposure apparatusfor producing microdevices) at which the produced photomask is used. Bymaking adjustment based on this, it is possible to form a pattern havingthe desired pattern shape in the state supported on the mask stage etc.of the device exposure apparatus.

Further, it is possible to detect the identification information formedon the master mask to obtain deformation information of the masksubstrate. By doing this, input of the deformation information becomesunnecessary, the number of work steps can be reduced, and occurrence ofdefective products due to input error etc. can be prevented. Further, itis possible to support the mask substrate at a plurality of pointswithout chucking. As the deformation information, it is possible to useinformation including information relating to flexing of the masksubstrate due to its own weight.

Note that when adjusting the relative positional relationship betweenthe pattern image and the mask substrate at the time of transfer of thepattern image, it is possible to make adjustments by for exampleshifting or rotating the position of the master mask and/or masksubstrate, shift the stepping position, change the scan speed, changethe scan direction, etc. Alternatively, it is possible to adjust theoptical characteristics by adjusting the projection characteristics ofthe pattern image, for example, the lens controller of the projectionoptical system projecting the pattern image.

An exposure apparatus of the present invention for working the abovemethod of exposure is an exposure apparatus provided with anillumination optical system (1) for irradiating illumination light to aplurality of master masks (Ri) formed by dividing an enlarged pattern ofa transfer pattern (27) and a projection optical system (3) for reducinga pattern image for each master mask and projecting it on a masksubstrate (4) on which the transfer pattern is to be formed, furthercomprising a detection device (56) for detecting information ondeformation of the mask substrate in accordance with a transfer positionof the pattern image and an adjustment device for adjusting at least oneof a relative positional relationship between the pattern image and themask substrate and projection characteristics of the pattern image atthe time of transfer of the pattern image based on the deformationinformation. In this case, it is possible to further provide a stage forsupporting the substrate at a plurality of points without chucking.

According to the exposure apparatus of the present invention, since theshape of the pattern image on the mask substrate is adjusted (deformed)for transfer, when projecting and exposing the patterns of the pluralityof masks successively on the substrate while stitching them, it ispossible to improve the continuity (continuity in the case of connectionin the direction along the lines in the case of for exampleline-and-space (L/S) patterns) and periodicity (periodicity ofarrangement in the direction orthogonal to the lines in the case of forexample L/S patterns) of the connecting parts of the patterns formedusing one master mask and another pattern formed using another adjoiningmaster mask. Due to this, it is possible to produce a high quality, highreliability photomask.

3. According to another aspect of the present invention, there isprovided a method for transfer of a pattern on to a substrate byexposing the substrate by illumination light through a mask formed withthe pattern, comprising supporting the substrate at a plurality ofpoints without chucking and adjusting at least one of a relativepositional relationship between the pattern and the substrate andtransfer conditions of the pattern at the time of transfer of thepattern based on information relating to flexing of the substrate by itsown weight corresponding to the transfer position of the pattern on thesubstrate. In this case; it is possible to employ, as transferconditions of the pattern, imaging characteristics of the projectionoptical system for forming a projected image of the pattern on thesubstrate. Also, said pattern is divided to more than one to be formedas a different mask and an exposure amount of said substrate can bechanged in accordance with a change amount of a line width of saidpattern image when transferring the pattern image on said substrate forevery said mask. In this case, said substrate becomes a working mask tobe used in an exposure apparatus for device production and an opticaltype reduction projection exposure apparatus can be used fortransferring said pattern image.

The exposure apparatus of the present invention for working the abovemethod of exposure is an apparatus for transferring a pattern to asubstrate by exposing the substrate by illumination light through a maskformed with the pattern, provided with a stage for supporting thesubstrate at a plurality of points without chucking and an adjustmentdevice for adjusting at least one of a relative positional relationshipbetween the pattern and the substrate and transfer conditions of thepattern at the time of transfer of the pattern based on informationrelating to flexing of the substrate by its own weight corresponding tothe transfer position of the pattern on the substrate.

4. According to still another aspect of the present invention, there isprovided an exposure method for irradiating illumination light on eachof a plurality of masks and transferring the pattern image on aphotosensitive layer on a substrate for every said mask, wherein anexposure amount of said photosensitive layer can be changed inaccordance with a change amount of a line width of said transferredpattern image at the time of transferring said pattern image at a partof said plurality of masks. In this case, said substrate becomes aworking mask to be used in an exposure apparatus for device productionand an optical type reduction projection exposure apparatus can be usedfor transferring said pattern image.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view provided for explaining the process of production of aworking reticle (photomask) of an embodiment of the present invention;

FIG. 2 is a view of the overall configuration of an optical typereduction projection exposure apparatus used when producing a workingreticle of an embodiment of the present invention;

FIG. 3 is a perspective view of key parts in the case of alignment of amaster reticle of an embodiment of the present invention;

FIG. 4 is a perspective view of key parts in the case of projecting onto a substrate a reduced image of a master pattern of a master reticleof an embodiment of the present invention;

FIG. 5 is a perspective view of key parts of a projection exposureapparatus for projecting on to a wafer a pattern of a working reticleproduced in an embodiment of the present invention;

FIG. 6A is a plan view of the configuration of a master reticle in anembodiment of the present invention;

FIG. 6B is a view of one example of a mask formed on a master reticle inan embodiment of the present invention;

FIG. 7 is a view of another example of a mask formed on a master reticlein an embodiment of the present invention;

FIG. 8 is a view of the configuration of a spatial image measurementapparatus in an embodiment of the present invention;

FIG. 9A is a view of the state of scanning of a projected image of amask for explaining spatial image measurement in an embodiment of thepresent invention;

FIG. 9B is a view of the output of a photoelectric sensor for explainingspatial image measurement in an embodiment of the present invention;

FIG. 9C is a view of a differential signal for explaining the spatialimage measurement in an embodiment of the present invention;

FIG. 10 is a view for explaining detection of a transfer position of amaster reticle in an embodiment of the present invention;

FIG. 11 is a view of the relationship among a master reticle (master),blank (photomask use substrate), and working reticle used in anembodiment of the present invention;

FIG. 12 is a view schematically showing the flexing accompanying supportof a blank in an embodiment of the present invention;

FIG. 13A is a view of the shape of a shot before deformation on thesurface of a substrate in an embodiment of the present invention; and

FIG. 13B is a view of the shape of a shot after deformation on thesurface of a substrate in an embodiment of the present invention.

BEST MODE FOR WORKING THE INVENTION

The present invention will be explained in further detail below withreference to the attached drawings.

FIG. 1 is a view of the process of production of a photomask of thisexample. In FIG. 1, the mask to be produced in this example is a workingreticle 34 used when producing a semiconductor device. This workingreticle 34 comprises a light transmitting substrate made of silica glassetc. on one surface of which is formed a master pattern 27 for transferfrom chrome (Cr), molybdenum silicide (MoSi₂ etc.), or another maskmaterial. Further, two alignment marks 24A and 24B are formed so as tostraddle this master pattern 27.

Further, the working reticle 34 is used in reduction projection of 1/β(where β is an integer or fraction larger than 1, for example, 4, 5, or6) through a projection optical system of an optical type projectionexposure apparatus. That is, in FIG. 1, a 1/β reduced image 27W of themaster pattern 27 of the working reticle 34 is exposed on each shot area48 on a wafer W coated with a photoresist, then developed and etched soas to form a predetermined circuit patter 35 on each shot area 48.Below, the explanation will be given of an example of a method ofproduction of a working reticle 34 as the photomask of this example.

In FIG. 1, first, a circuit pattern 35 of a certain layer of thesemiconductor device to be finally produced is designed. The circuitpattern 35 forms various line-and-space patterns (or isolated patterns)in a rectangular area with widths of perpendicularly intersecting sidesof dX and dY. In this example, the circuit pattern 35 is enlarged β-foldand the master pattern 27 comprised of a rectangular area of widths ofperpendicular sides of β·dx and β·dY is formed in the image data of acomputer. The β is the reciprocal of the reduction magnification (1/β)of the projection exposure apparatus in which the working reticle 34 isused. Further, when inversely projected, the image is enlarged inverted.

Next, the master pattern 27 is enlarged α-fold (α is an integer orfraction larger than 1, for example, 4, 5, 6, etc.) and a master pattern36 comprised of a rectangular area with widths of perpendicular sides ofα·β·dx and α·β·dY is prepared on the image data. The master pattern 36is divided into a number of sections in the vertical and horizontaldirections to prepare a x α number of master patterns P1, P2, P3 . . .PN (N=α²) on the image data. In FIG. 1, the case where α=5 is shown.Note that the divisor a of the master pattern 36 does not necessarilyhave to match with the magnification a from the master pattern 27 to themaster pattern 36. Next, the drawing data for the electron beamlithography system (a laser beam lithography system etc. also may beused) is created by the master patterns Pi (i=1 to N). The masterpatterns Pi are transferred on the master reticles Ri used as the mastermask by equal magnification.

For example, when producing one master reticle R1, a thin film of chromeor molybdenum silicide or another mask material is formed on a lighttransmitting substrate of silica glass etc., an electron beam resist iscoated on this, then an electron beam lithography system is used fordrawing an equal magnification image of the first master pattern P1 onthe electron beam resist. Next, the electron beam resist is developed,then etched and the resist peeled off to form the master pattern P1 onthe pattern area 20 on the master reticle R1. At this time, alignmentmarks 21A and 21B comprised of two 2-dimensional marks are formed atpredetermined positional relationships with respect to the masterpattern P1 on the master reticle R1. Similarly, the master patterns Piand alignment marks 21A and 21B are formed using an electron beamlithography system etc. on other master reticles Ri. These alignmentmarks 21A and 21B are used for positioning at the time of the laterstitching. Further, while explained in detail later, a plurality ofmarks (marks for spatial image measurement, reticle identification,etc.) are formed in the peripheral area (light blocking area outside ofthe pattern area formed with the pattern) of the master reticles Ri.

In this way, in this example, since the master patterns Pi drawn by theelectron beam lithography system (or laser beam lithography system) arepatterns enlarged α-fold from the master pattern 27, the amount of thedrawing data is reduced to about 1/α² of the case of direct drawing ofthe master pattern 27. Further, the minimum line width of the masterpatterns, Pi is α-times (for example, 5 times or 4 times etc.) theminimum line width of the master pattern 27, so the master patterns Pican be drawn in a short time and at a high accuracy by an electron beamlithography system using a conventional electron beam resist. Further,once producing N number of master reticles R1 to RN, they can berepeatedly used as later explained to produce the necessary number ofworking reticles 34, so the time for producing the master reticles R1 toRN does not become a large burden.

That is, the working reticle 34 is produced by transferring the 1/αreduced images PIi (i=1 to N) of the master patterns Pi of the N numberof master reticles Ri while stitching them. Note that it is alsopossible not to divide the master pattern 36 into a matrix likeplurality of master patterns Pi as shown in FIG. 1, but for example todivide it for example for each functional block (CPU, DRAM, A/Dconverter, D/A converter, etc.) This is effective for producing aworking reticle for a system LSI. That is, even with system LSIs ofdifferent applications or performance, parts of the circuit are designedin common. It is possible to apply master patterns (master reticles)corresponding to these common circuits to the production of thedifferent system LSIs and therefore reduce the total number of masterreticles.

FIG. 2 shows a reduction projection exposure apparatus used whenproducing a working reticle 34. In FIG. 2, at the time of exposure,illumination light IL is irradiated on the reticle on the reticle stage2 from an illumination system 1 comprised of an exposure light source, afly-eye lens or rod integrator or other optical integrator (homogenizer)for achieving a uniform luminance distribution, an illumination systemaperture stop, a reticle blind (variable field stop), a condenser lens,etc. The i-th (i=1 to N) master reticle Ri is placed on the reticlestage 2 of this example. Note that as the exposure light, i-rays(wavelength 365 nm) of a mercury lamp or other emission line, KrFexcimer laser light (wavelength 248 nm), ArF excimer laser light(wavelength 193 nm), F₂ laser light (wavelength 157 nm), etc. may beused.

The image of the pattern in the illuminated area of the master reticleRi is projected on the surface of the substrate (blank) 4 for theworking reticle 34 by a reduction magnification 1/α (α is for example 5,4, etc.) through the projection optical system 3. The substrate 4 is alight transmitting substrate such as silica glass. A thin film ofchrome, molybdenum silicide, or other mask material is formed on thepattern area 25 of the surface (see FIG. 4). Alignment marks 24A and 24Bcomprised of two 2-dimensional marks for positioning are formed so as tostraddle the pattern area 25. These alignment marks 24A and 24B areformed in advance before transfer of the master pattern using anelectron beam lithography system, laser beam lithography system,projection exposure apparatus (stepper, scanner), etc. Further, aphotoresist is coated on the surface of the substrate 4 so as to coverthe mask material. Below, the explanation will be made with reference toa Z-axis taken parallel to the optical axis AX of the projection opticalsystem 3, to an X-axis in the plane perpendicular to the Z-axis andparallel to the paper surface of FIG. 2, and to a Y-axis perpendicularto the paper surface of FIG. 2.

First, the reticle stage 2 positions the master reticle Ri on it in theXY plane. The position and rotational angles (amounts of rotation aboutthe X-axis, Y-axis, and Z-axis) of the reticle stage 2 are measured by anot shown laser interferometer and the operation of the reticle stage 2is controlled by the measured values and the control information fromthe main control system 9. On the other hand, the substrate 4 issupported by vacuum chucking or supported at three points on a not shownsubstrate holder, the substrate holder is fixed on the sample table 5,and the sample table 5 is fixed on the XY stage 6. The sample table 5brings the surface of the substrate 4 in register with the image planeof the projection optical system 3 by controlling the focus position(position in optical axis AX direction) and tilt angle of the substrate4 by the auto focus system. Further, the XY stage 6 is driven on thebase 7 by for example a linear motor and positions the sample table 5(substrate 4) in the X-direction and Y-direction.

The X-coordinate, Y-coordinate, and rotational angles (amounts ofrotation about the X-axis, Y-axis, and Z-axis) are measured by a movingmirror 8m fixed above the sample table 5 and a laser interferometer 8arranged facing it. The measured values are supplied to the stagecontrol system 10 and main control system 9. The moving mirror 8m, asshown in FIG. 3, is a general name for the X-axis moving mirror 8mX andY-axis moving mirror gmY. The stage control system 10 controls theoperation of the linear motor of the XY stage 6 etc. based on themeasured values and the control information from the main control system9.

Further, in the present example, a shelf-like reticle library (maskmagazine) 16 is arranged at the side of the reticle stage 2. Masterreticles R1, R2, . . . , RN are carried on the N number of supportshelves 17 successively arranged in the Z-direction in the reticlelibrary 16. These master reticles R1 to RN are reticles (master masks)formed with master patterns P1 to PN obtained by dividing the masterpattern 36 of FIG. 1. The reticle library 16 is supported movably in theZ-direction by a slider 18. A reticle loader 19 able to freely rotateand provided with an arm able to move in a predetermined range in theZ-direction is arranged between the reticle stage 2 and the reticlelibrary 16. The main control system 9 adjusts the position of thereticle library 16 in the Z-direction through the slider 18, thencontrols the operation of the reticle loader 19 to enable transfer ofdesired master reticles R1 to RN between the desired support shelves 17of the reticle library 16 and the reticle stage 2. In FIG. 2, the i-thmaster reticle Ri in the reticle library 16 is placed on the reticlestage 2.

Further, a magnetic disk drive or other storage device 11 is connectedto the main control system 9. An exposure data file is stored in thestorage device 11. The exposure data file stores identificationinformation (ID information etc.) given to the master reticles R1 to RNused for production for each working reticle and reticle informationrelating to the master reticle corresponding to the identificationinformation (exposure conditions, various correction values, etc.)

At the time of exposure of the substrate 4 of this example, whenexposure of a reduced image of a master reticle (for example, R1) havinga master pattern to be transferred to one shot area on the substrate 4on that shot area is finished, the master reticle R1 on the reticlestage 2 is returned to the reticle library 16 through the reticle loader19, then the next master reticle to be transferred (for example R2) isplaced from the reticle library 16 through the reticle loader 19 on thereticle stage 2. In this state, the later mentioned alignment, detectionof the identification marks etc., correction of the imagingcharacteristics, etc. are performed and the shot area on the substrateto which the master reticle R2 is to be transferred is moved to theexposure area of the projection optical system 3 by step movement of theXY stage 6. Next, a reduced image of the master reticle R2 is projectedand exposed on the shot area on the substrate 4 through the projectionoptical system 3, then reduced images of the corresponding masterreticles R2 to RN are successively exposed on the remaining shot areason the substrate 4 by the step-and-repeat system.

When exposing reduced images of the master reticles R1 to RN on thesubstrate 4 in this way, it is necessary to stitch adjoining reducedimages at a high accuracy. Therefore, the master reticles Ri (i=1 to N)and the corresponding shot areas (Si) on the substrate have to bealigned at a high accuracy. For this alignment, a reticle and substratealignment mechanism is provided at the projection exposure apparatus ofthis example.

FIG. 3 shows the reticle alignment mechanism of this example. In FIG. 3,a light transmitting; fiducial mark member 12 is affixed near thesubstrate 4 on the sample table 5. Two cross-shaped fiducial marks 13Aand 13B are for example formed at a predetermined interval in theX-direction on the fiducial mark member 12. At the bottoms of thefiducial marks 13A and 13B is placed an illumination system forilluminating the fiducial marks 13A and 13B at the projection opticalsystem 3 side by illumination light branched from the exposure light IL.When aligning a master reticle Ri, the substrate stage 6 of FIG. 3 isdriven to position the fiducial marks 13A and 13B so that the centerpoint between the fiducial marks 13A and 13B on the fiducial mark member12 substantially registers with the optical axis AX of the projectionoptical system 3 as shown in FIG. 3.

Further, for example, two cross-shaped alignment marks 21A and 21B areformed so as to straddle the pattern area 20 of the pattern surface(bottom surface) of the master reticle Ri in the X-direction. Thedistance between the fiducial marks 13A and 13B is set to besubstantially equal to the distance between images of the alignmentmarks 21A and 21B reduced by, the projection optical system 3. Byillumination by illumination light of the same wavelength as theexposure light IL from the bottom of the fiducial mark member 12 in thestate with the center point between the fiducial marks 13A and 13Bsubstantially in register with the optical axis AX in the above way,images of the fiducial marks 13A and 13B enlarged by the projectionoptical system 3 are formed near the alignment marks 21A and 21B of themaster reticle Ri.

Mirrors 22A and 22B are arranged above the alignment marks 21A and 21Bto reflect the illumination light from the projection optical system 3side in the ±X directions. Image processing type alignment sensors 14Aand 14B are provided by a TTR (through-the-reticle) system so as toreceive the illumination light reflected by the mirrors 22A and 22B. Thealignment sensors 14A and 14B are each provided with an imaging systemand a 2-dimensional image pickup element such as a CCD camera. The imagepickup elements pick up the images of the alignment marks 21A and 21Band the corresponding fiducial marks 13A and 13B and supply imagesignals to an alignment signal processing system 15 of FIG. 2.

The alignment signal processing system 15 processes the image signals tofind the amount of positional deviation of the alignment marks 21A and21B in the X-direction and Y-direction with respect to the fiducialmarks 13A and 13B and supplies the two positional deviations to the maincontrol system 9. The main control system 9 positions the reticle stage2 so that the two positional deviations become symmetrical and withinpredetermined ranges. Due to this, the alignment marks 21A and 21B andin turn the master pattern Pi in the pattern area 20 of the masterreticle Ri (see FIG. 1) are positioned with respect to the fiducialmarks 13A and 13B.

In other words, the center (exposure center) of the reduced image of themaster pattern Pi of the master reticle Ri obtained by the projectionoptical system 3 is positioned at the center point between the fiducialmarks 13A and 13B (substantially the optical axis AX) and theperpendicularly intersecting sides of the contour of the master patternPi (contour of pattern area 20) are set to be parallel to the X-axis andY-axis. In this state, the main control system 9 of FIG. 2 stores theX-direction and Y-direction coordinates (XF₀,YF₀) of the sample table 5measured by the laser interferometers 8, whereby the alignment operationof the master reticle Ri ends. After this, it is possible to move anypoint on the sample table 5 to the exposure center of the master patternPi.

Further, as shown in FIG. 2, an image processing type alignment sensor23 is provided by an off-axis system at the side of the projectionoptical system 3 to detect the position of a mark on the substrate 4.The alignment sensor 23 illuminates a detection mark by illuminationlight of a wide band to which the photoresist is not sensitive, picks upthe image of the detection mark by a 2-dimensional image pickup elementsuch as a CCD camera, and supplies an image signal to the alignmentsignal processing system 15. Further, the distance (base line amount)between the detection center of the alignment center 23 and the centerof the projected image of the pattern of the master reticle Ri (exposurecenter) is found in advance using a predetermined fiducial mark on thefiducial mark member 12 and stored in the main control system 9.

As shown in FIG. 3, two cross-shaped alignment marks 24A and 24B areformed at the ends of the substrate 4 in the X-direction. After themaster reticle Ri is aligned, the XY stage 6 is driven to successivelymove the fiducial marks 13A and 13B and the alignment marks 24A and 24Bon the substrate 4 to the detection area of the alignment sensor 23 ofFIG. 3 and measure the positional deviations of the fiducial marks 13Aand 13B and the alignment marks 24A and 24B with respect to thedetection center of the alignment sensor 23. The results of themeasurements are supplied to the main control system 9. Using thesemeasurement results, the main control system 9 finds the coordinates(XP₀,YP₀) of the sample table 5 when the center point between thefiducial marks 13A and 13B is in register with the detection center ofthe alignment sensor 23 and the coordinates (XP₁, YP₁) of the sampletable 5 when the center point between the alignment marks 24A and 24B isin register with the detection sensor of the alignment sensor 23. Thisends the alignment operation of the substrate 4.

As a result, the distances between the center point between the fiducialmarks 13A and 13B and the center point between the alignment marks 24Aand 24B in the X-direction and the Y-direction become (XP₀-XP₁,YP₀-YP₁).Therefore, by driving the substrate stage 6 of FIG. 2 by exactly thedistances (XP₀-XP₁, YP₀-YP₁) with respect to the coordinates (XF₀,YF₀)of the sample table 5 at the time of alignment of the master reticle Ri,it is possible to bring the center point between the alignment marks 24Aand 24B of the substrate 4 (center of substrate 4) into register withthe center point between the projected images of the alignment marks 21Aand 21B of the master reticle Ri (exposure center) with a high accuracyas shown in FIG. 4. From this state, the XY stage 6 of FIG. 2 may bedriven to move the sample table 5 in the X-direction and the Y-directionso as to expose a reduced image PIi of a master pattern Pi of the masterreticle Ri at a desired position with respect to the center of thesubstrate 4.

That is, FIG. 4 shows the state where a master pattern Pi of an i-thmaster reticle Ri is reduced and transferred on to the substrate 4through the projection optical system 3. In FIG. 4, a rectangularpattern area 25 surrounded by sides parallel to the X-axis and Y-axis isvirtually set in the main control system 9 centered on the center pointbetween the alignment marks 24A and 24B of the surface of the substrate4. The size of the pattern area 25 is the size of the master pattern 36of FIG. 1 reduced to 1/α. The pattern area 25 is partitioned equallyinto a sections in the X-direction and the Y-direction to virtually setshot areas S1, S2, S3, . . . , SN (N=α²). The position of a shot area Si(i=1 to N) is set to the position of a reduced image PIi of the i-thmaster pattern Pi when assuming reducing and projecting the masterpattern 36 of FIG. 1 through the projection optical system 3 of FIG. 4.

Further, when the imaging characteristics of the projected image of theprojection exposure apparatus using the working reticle 34 of thepresent example are ideal, the main control system 9 drives the XY stage6 of FIG. 2 so as to bring the center of the i-th shot area Si on thesubstrate 4 in FIG. 4 into register with the exposure center of thereduced image PIi of the master pattern Pi of the master reticle Rifound by the above alignment. Next, the main control system 9 performsprocessing for correcting the imaging characteristics explained later,then projects and exposes the reduced image of the master pattern Pi onthe shot area Si of the substrate 4. In FIG. 4, the reduced image of amaster pattern already exposed in the pattern area 25 of the substrate 4is shown by a solid line, while an unexposed reduced image is shown by abroken line.

In this way, by successively exposing the reduced images of the masterpatterns P1 to PN of the N number of master reticles R1 to RN of FIG. 2on the corresponding shot areas Si to SN on the substrate 4, the reducedimages of the master patterns P1 to PN are exposed while being stitchedwith the reduced images of the adjoining master patterns. Due to this, aprojected image 26 reduced 1/α from the master pattern 36 of FIG. 1 isexposed. Next, the photoresist on the substrate 4 is developed andetched and the remaining resist pattern is peeled off, whereby theprojected image 26 on the substrate becomes the master pattern 27 asshown in FIG. 5 and the working reticle 34 is completed.

When exposing one substrate 4, regardless of the exchange of a masterreticle Ri, the substrate 4 is fixed to the sample table 5. Thisposition is measured accurately by the laser interferometer 8.Therefore, during exposure of one substrate 4, the positionalrelationship between the fiducial marks 13A and 13 b and the substrate 4will not change, so at the time of exchange of the master reticle Ri, itis sufficient to position the master reticle Ri with respect to thefiducial marks 13A and 13B. It is not necessarily required to detect thepositions of the alignment marks 24A and 24B on the substrate 4 for eachmaster reticle. In this case as well, the master patterns Pi on themaster reticles Ri are exposed while maintaining an accurate positionalrelationship by positioning of the fiducial marks 13A and 13B andpositional control of the XY stage 6 by the stage control system 10monitored by the laser interferometer. Therefore, the stitching accuracyamong patterns of course also becomes a high accuracy.

Further, when for example dense patterns and isolated patterns areformed on the master pattern 27 of FIG. 1, only the dense patterns areformed on the first master reticle Ra among the master reticles R1 toRN, while only isolated patterns are formed at another master reticleRb. At this time, the best illumination conditions, imaging conditions,and other exposure conditions differ between the dense patterns and theisolated patterns, so it is also possible to optimize the exposureconditions, that is, the shape and size of the aperture stop in theillumination system 1, the coherence factor (σ value), the numericalaperture of the projection optical system 3, etc. in accordance with themaster pattern Pi for each exposure of the master reticle Ri. At thistime, when the master pattern Pi is a dense pattern (periodic pattern),it is sufficient to employ the deformation illumination method and limitthe shape of the secondary light source to a annular shape or aplurality of local areas substantially equal distances away from theoptical axis of the illumination system. Further, to optimize theexposure conditions, it is also possible to attach an optical filter(so-called pupil filter) blocking exposure light in a circular areacentered about the optical axis near the pupil plane of the projectionoptical system 3 and/or jointly use the so-called cumulative focusmethod (flex method) causing relative vibration in a predetermined rangebetween the image plane of the projection optical system 3 and substrate4. Whether or not to apply techniques for optimizing the exposureconditions or the parameters etc. for the same are set for each masterreticle Ri as reticle information in the exposure data file of thestorage device 11. At the time of exposure, optimization is performed inaccordance with the reticle information corresponding to the masterreticle Ri of the exposure data file.

Note that it is also possible to use the master mask as a phase shiftmask and make the σ-value of the illumination system for example 0.1 to0.4 or, if necessary, to jointly use the above cumulative focus methodor employ it alone. Further, the photomask (working reticle) is notlimited to a mask comprised of only a chrome or other light blockinglayer. It may also be a phase shift mask of for example the spatialfrequency modulation type (Shibuya-Levenson type), edge emphasizingtype, and halftone type. In particular, in the spatial frequencymodulation type or edge emphasizing type, a master mask for a phaseshifter is separately prepared for patterning a phase shifter overlaidon a light blocking pattern on the mask substrate.

Next, a detailed explanation will be given of a master reticle Ri in theembodiment of the present invention. In the following explanation, forsimplification, the explanation will be made of production of a workingreticle using four master reticles. As shown in FIG. 6A, the lightblocking area (peripheral area) 52 outside of the area 51 where thepattern (device pattern) of the master reticle Ri is formed (patternarea) is formed with two alignment marks 21A and 21B, while theperipheral area 52 is further formed with a plurality of first masteridentification marks M1 and second master identification marks M2.

The first master identification mark M1, in the present embodiment, is amark for indicating transfer position information showing the positionon the substrate 4 to which the master reticle Ri is to be transferredand a mark for spatial image measurement for finding by parameters usedfor various correction processing by spatial image measurement. Thefirst master identification mark M1 is not particularly limited innumber or position, but in this embodiment, two each are arranged ateach of the sides (boundary line parts of pattern area 51 and peripheralarea 52) of the pattern area 51.

Each of the first master identification marks M1, as shown in FIG. 6B,has four display areas of the top right RU, bottom right RD, top leftLU, and bottom left LD and a pair of mark elements 53X and 53Y displayedat one of these. The mark elements 53X and 53Y are comprised ofline-and-space patterns comprised of a plurality of slits intermittentlyarranged. The longitudinal direction of the slits of the mark element 53and the longitudinal direction of the slits of the mark element 53Y areformed to perpendicularly intersect each other.

Further, the four display areas RU, RD, LU, and LD are for showing thepositions on the substrate 4 where the master reticle Ri is to betransferred. The positions at which the mark elements 53X and 53Ycomprised of the line-and-space patterns are formed show the position onthe mask substrate 4 where the pattern image of the master reticle Ri isto be transferred. That is, the master reticle of FIG. 6A means thepattern to be transferred on the top right area on the substrate 4 isformed. Here, the explanation is given taking as an example the case ofproduction of a working reticle 34 by four master reticles Ri. Thetransfer position is identified by the four display areas RU, RD, LU,and LD. When producing a working reticle from a greater number of masterreticles, it should be identified by columns and rows in the exposuremap at the time of exposure on the substrate 4.

Note that the mark element of the first master identification mark M1 iscomprised of the pair of mark elements 53X and 53Y here, but may also becomprised of a single mark element or, as shown in FIG. 7, may becomprised of a combination of a plurality of mark elements 53X1, 53X2,53X3, 53Y1, 53Y2, 53Y3, 53A, 53B, and 53C. The mark element may bearrangements 53X1 to 3 and 53Y1 to 3 of slits and also matrixarrangements 53A to C of a plurality of pinholes (including circular,rectangular, or other shapes). Further, the mark element may also be acombination of slits of different thicknesses (widths) or intervals ofarrangement such as 53X1 to 3 or 53Y1 to 3 or pinholes of differentsizes (diameters etc.) or intervals of arrangement such as 53A to C.

For the configuration of the mark element of the first masteridentification mark M1, it is possible to use one of the shapecorresponding to the pattern Pi formed on the pattern area 51. When thepattern Pi is a line-and-space pattern, use should be made of thearrangement of slits 53X1 to 3 and 53Y1 to 3, while when the pattern Piis an isolated pattern or a contact hole (C/H) pattern, use should bemade of an arrangement of isolated patterns (not shown) or pinholes 53Ato C. If the first master identification mark M1 differs in shapebetween the master reticles Ri, this is sometimes not desirable from theviewpoint of standardization etc. Therefore, it is possible to use acombination of a plurality of types of mark elements as shown in FIG. 7and to make measurements by selecting and combining corresponding markelements in accordance with the shape or type of the pattern formed onthe pattern area 51.

Further, the second master identification mark M2, as shown in FIG. 6A,is a bar code mark formed on a light blocking area 52 of the masterreticle Ri. The bar code is a mark set with identification information(ID number etc.) for identification of one master reticle Ri fromanother master reticle. The storage device 11 (exposure data file) ofFIG. 2 is set with reticle information relating to the master reticle Ricorresponding to the identification information given to the pluralityof master reticles Ri.

As the reticle information, for example, the name of the product, thename of the layer, the various exposure conditions (exposure times forvarious mask reticles Ri, focus position, blind size, illuminationconditions, shot magnification, etc.), various correction information(correction values for canceling deformation accompanying support of themaster reticle Ri, aberration of the projection optical system PL, anddeformation accompanying support of the blank) are set. Note that it isalso possible to set transfer position information indicating theposition on the substrate 4 to which the pattern of the master reticleRi is to be transferred in the reticle information, but here thetransfer position information is set in the first master identificationmark M1, so this may or may not be included in the reticle information.

These first master identification marks M1 and second masteridentification marks M2 are formed using an electron beam lithographysystem, laser beam lithography system, projection exposure apparatus(stepper or scanner), etc. simultaneously with or by a separate processfrom the formation of the alignment marks 21A and 21B.

Next, an explanation will be made of measurement of the marks formed onthe master reticle. First, the spatial image measurement using the firstmaster identification marks (spatial image measurement marks) isperformed as follows. Note that spatial image measurement is disclosedin for example Japanese Unexamined Patent Publication (Kokai) No.8-83753 and its corresponding U.S. Pat. No. 5,650,840 or JapaneseUnexamined Patent Publication (Kokai) No. 9-153448 and its correspondingU.S. Pat. No. 5,841,520. The disclosure of these publications and theU.S. patents are incorporated by reference and made part of thedisclosure of this description in so far as allowed by the domestic lawsof the designated countries or elected countries designated or electedin this international application. FIG. 8 shows a spatial imagemeasurement apparatus. In FIG. 8, a light receiver for measuring theimage of the first master identification mark M1, formed on theperipheral area 52 of the master reticle Ri, projected by the projectionoptical system is provided on the XY stage 6. This light receiver iscomprised of a photoelectric sensor (photoelectric conversion element)56 provided below a light receiving plate 55 having an aperture 54 of arectangular shape (in this embodiment, a square shape) as illustrated.The output signal of the photoelectric sensor 56 is input to the maincontrol system 9. Note that it is also possible not to provide thephotoelectric sensor 56 under the aperture 54, but to guide the light bya light guide etc. and detect the projected image by a photoelectricsensor etc. at another portion (for example, outside the XY stage 6).

Illuminating the master reticle Ri, an image of the first masteridentification mark M1 (mark element 53X or 53Y) projected by theprojection optical system 3 is formed on the surface of the lightreceiving plate 55. In the state with the XY stage 6 moved by the maincontrol system 9 to bring the light receiver of the spatial imagemeasurement apparatus near the position corresponding to one of theprojected images of the first master identification marks M1, as shownin FIG. 9A, the aperture 54 of the light receiver is moved over (scans)the projected image 57, whereby a signal such as shown in FIG. 9B isdetected by the photoelectric sensor 56. That is, the leading slit imagein the scan direction among the plurality of slits of the first masteridentification mark M1 appears in the aperture 54, the adjoining slitimages successively appear in the aperture 54, all of the slit imagesappear in the aperture 54, then they successively move out of theaperture 54 until finally all of the slit images move out of theaperture 54.

At this time, as shown in FIG. 9B, the output (amount of light received)I of the photoelectric sensor 56 increases in steps, peaks, thendecreases in steps along with movement of the projected images 57 of theslits through the aperture 54. Next, by finding the differential signal(dI/dx) of FIG. 9B to detect the coordinate position of the XY stage atthe center point of the signal waveform shown in FIG. 9C, it is possibleto measure the position of the projected image of the first masteridentification mark M1 in the X-direction (or Y-direction). Further,this measurement may be performed at a plurality of Z-positions todetect the position in the Z-direction where the intensity of thedifferential signal peaks so as to detect the imaging plane (focalposition). Therefore, by making the stage move in the Z-direction andX-direction or the Y-direction alone or at a tilt, it is possible todetect the projected image at the optimal imaging plane and possible toimprove the accuracy of the detection. The spatial image measurementusing the first master identification mark M1 is performed afteralignment of the reticle Ri by the reticle alignment marks 21A and 21B.The results of the measurement are stored and held in the storage device11.

Further, for detection of the transfer positional information using thefirst master identification marks (transfer position display marks) M1,the above spatial image measurement apparatus is used or a simplemeasurement apparatus having a separately provided photoelectric sensoretc. is used, as shown in FIG. 10, to scan two locations in theX-direction ((1) and (2)) and two locations in the Y-direction ((3) and(4)) and detect at which scan a signal from a mark is detected. That is,by detecting at which of the four display areas RU, RD, LU, and LD ofthe first master identification mark M1 the mark elements 53X and 53Yare formed, the position on the substrate 4 where the pattern image ofthe master reticle Ri is to be transferred is detected. For example, inthe case where a signal is obtained from the scan positions (1) and (4)(case of FIG. 10), it is recognized that the master reticle is forexposure at the top right on the substrate 4. Note that regarding thedetection of the first master identification marks M1 for obtaining thetransfer position information, it is not necessary to detect all of thefirst master identification marks M1 on the master reticle Ri. It issufficient to detect one of them.

The second master identification mark (bar code mark) M2 is read by anot shown bar code reader. The exposure data file of the storage device11 is searched through based on the identification information indicatedby the bar code read by the bar code reader and the correspondingreticle information is extracted.

Next, refer to FIG. 11. Here, for simplification, the explanation willbe given taking as an example the case of production of a workingreticle 34 using the four master reticles (masters 1 to 4) R1 to R4. Asshown in the figure, a working reticle 34 is produced by transferringand forming patterns of the masters 1 to 4 on corresponding positions onthe substrate (blank) 4. Note that the transfer position information bythe first master identification mark M1 of the masters 1 to 4 are thetop right RU for the master 1, the top left LU for the master 2, thebottom left LD for the master 3, and the bottom right RD for the master4. Further, the operator (worker) is assumed to recognize that theproduct name or layer name etc. of the working reticle to be produced is“256 MB DRAM, fourth generation, wiring 1 process) and that one workingreticle is produced from four master reticles R1 to R4.

The operator specifies the four masters 1 to 4 for the “256 MB DRAM,fourth generation, wiring 1 process” from the reticle storage room andsets them in the reticle library 16 of the reticle exposure apparatus.At this time, there is no need to consider at all the positions on thesubstrate 4 to be exposed on by the masters 1 to 4, the order, thecorresponding exposure conditions, the correction values, etc. It issufficient to simply suitably set them. For example, there is notnecessarily a need for setting the masters 1 to 4 in the order of 1, 2,3, and 4. An order of 1, 2, 4, and 3 or another order is also possible.

When the operation of the reticle exposure apparatus is started, any onemaster (at this point, which master is unclear) is loaded from thereticle library 16 on to the reticle stage 2. For the master on thereticle stage 2, alignment including measurement of the alignment marks21A and 21B, detection and measurement of the first masteridentification mark M1 including detection of the transfer positioninformation and spatial image measurement, and detection of the secondmaster identification mark M2 for detection of the identificationinformation are performed. The position on the substrate 4 (step pitchX, Y) to which the master is to be transferred is specified by thetransfer position information detected from the first masteridentification mark M1, and the corresponding reticle information isextracted from the storage device (exposure data file) 11 based on theidentification information detected from second master identificationmark M2. The various parameters (for example, the exposure time, focusposition, illumination conditions, shot XY magnification correctionvalues, etc.) are set based on the reticle information.

Based on the results of the spatial image measurement of the firstmaster identification mark M1, the various correction values of the shotdistortion, shot XY magnification, shot rotation, etc. are calculated bypredetermined calculation using the least square method etc. andcorresponding correction values are set in a corresponding device(leveling device, magnification adjustment device, etc.) for thesecorrections so that the amount of deviation of the position of theprojected image of the first master identification mark M1 (imageposition) from the corresponding ideal lattice (position in design)becomes smaller.

When the master is for example the master 1, the transfer positioninformation of the first master identification mark M1 is the top rightRU, so the XY stage 6 is positioned in accordance with the result ofdetection of the first master identification mark M1 and exposure isperformed in accordance with various exposure conditions. Next, the nextmaster is exchanged and similar exposure performed to form a pattern onthe substrate 4 while stitching. In this way, the reticle exposureapparatus successively loads four masters on the reticle stage 2 one ata time, detects the first and second master identification marks M1 andM2 of the master loaded on the reticle stage 2, finds the transferpositions on the substrate 4 and the various exposure conditions, andexposes accordingly to produce the working reticle 34.

As one example of the correction information set in the exposure datafile of the above storage device 11, an explanation will be given belowof flexing accompanying support of the substrate (blank) 4. Thesubstrate 4 supported (held) on the substrate holder on the sample table5 of the reticle exposure apparatus deforms in accordance with thesupport method such as three-point support, four-point support, pointcontact, facial contact, mechanical clamping, vacuum chucking, simpleplacement, support positioning, etc., the thickness, size, and othershapes and materials of the substrate 4 and for example flexes due toits own weight with three-point support etc.

Further, FIG. 12 schematically shows the state of the substrate 4flexing due to its own weight when simply placed by three-point contact.If taking note of for example a square shot area of the substrate 4, inthe state of flexing due to support, the shot deforms as shown by SH1 inthe figure. Even if the pattern is transferred and formed accurately inthat state, when returning to the ideal state free from flexing afterbeing released from the three-point support, the deformation of the shotdisappears as shown by SH2 in the figure and conversely distortionoccurs in the pattern transferred and formed.

To eliminate this distortion of the pattern and transfer and form apattern of an ideal shape, it is sufficient to perform exposure in astate giving pre-distortion to the projected image so as to cancel thatdistortion. For example, when the square shot shown in FIG. 13A deformsto the shape shown in FIG. 13B, at least one of the exposure conditions,for example, the lens controller for moving the optical elements of theoptical system 3, reticle rotation, stepping position, scan speed, scandirection, etc., are adjusted so that the square shot shown in FIG. 13Abecomes the shape shown in FIG. 13B.

Specifically, the procedure is as follows: In the state with thesubstrate 4 supported by a support method the same as the support methodin the reticle exposure apparatus (FIG. 2), the amount of deformationfrom an ideal position of the surface of the substrate 4 (here, a pointin a state assuming no flexing) is found by actual measurement at nnumber of points (n is an integer greater than 1) in the shot area to beexposed using the corresponding master or is found by calculation(simulation) and the results made (dxi,dyi). Here, i=1 to n. Here,considering a model where the point (x,y) of the surface of thesubstrate displaces to the point (X,Y) due to the deformation of theshot (magnification, rotation, orthogonality, and offset), the followingequation (1) is obtained: $\begin{matrix}{\begin{bmatrix}X \\Y\end{bmatrix} = {\begin{bmatrix}a & b \\c & d\end{bmatrix} = {\begin{bmatrix}x \\y\end{bmatrix} = \begin{bmatrix}e \\f\end{bmatrix}}}} & (1)\end{matrix}$

Here, a=(shot area magnification X)−1, b=−(shot magnificationX)×(rotation+orthogonality), c=(shot magnification Y)×(rotation),d=(shotmagnification Y)−1, e=(offset X), and f=(offset Y).

To find the deformation of the shot area, it is sufficient to find thea, b, c, d, e, and f giving the minimum E of the following equation (2)by the least square method:

E=Σ[(Xi−dxi)²+(Yi−dyi)²] . . .  (2)

The correction values a to f are found for each master reticle Ri andset in the exposure data file of the storage device 11. Based on this,the lens controller, reticle rotation, stepping position, and the likeare finely adjusted to cause the projected image to deform as desiredfor exposure. Due to this, it is possible to reduce the error occurringdue to deformation of the substrate 4, for example, flexing accompanyingsupport, and possible to form a pattern with a higher accuracy. Notethat here, the correction values a to f were calculated based on theamounts of deformation from the ideal shape of the substrate 4, but in adevice exposure apparatus where the working reticle 34 produced usingthis substrate 4 is used, it is also possible to calculate thecorrection values a to f based on the amounts of deformation from theshape in the state where the working reticle 34 is supported and fromthe shape in other states.

Note that above an explanation was made of deformation of the substrate4, but it is also possible to store and hold correction values forcanceling or reducing the deformation occurring due to flexingaccompanying support of the master reticle Ri, distortion or comaaberration or other aberration of the projection optical system 3,drawing error of the pattern of the master reticle Ri, or other error inan exposure data file of the exposure apparatus 11 and refer to thisdata based on identification information of the master reticle Ri(second master identification mark M2) to suitably correct the imagingcharacteristics (including focusing). Note that the correction valuesare found by actual measurement or calculation (simulation).

Next, an explanation will be made of an example of the operation in thecase of exposure using the working reticle 34 of FIG. 1 produced in theabove way.

FIG. 5 shows key parts of a reduction projection type exposure apparatus(device exposure apparatus) mounting a working reticle 34. In FIG. 5, awafer W is arranged at the bottom surface of the working reticle 34 heldon a not shown reticle stage through a projection optical system 42having a reduction magnification 1/β (β is 5, 4, etc.) A photoresist iscoated on the surface of the wafer W. The surface is held to be inregister with the image plane of the projection optical system 42. Thewafer W is held on the sample table 43 through a not shown wafer holder,while the sample table 43 is fixed on an XY stage 44. By driving the XYstage 44 based on the coordinates measured by the movable mirrors 45mXand 45mY on the sample table 43 and the corresponding laserinterferometers, the wafer W is positioned.

Further, a fiducial mark member 46 formed with fiducial marks 47A and47B is fixed on the sample table 43. The working reticle 34 is formedwith alignment marks 24A and 24B so as to straddle the pattern area 25in the X-direction. When the alignment marks 24A and 24B are alignmentmarks for transferring a pattern on to a pattern area 25 of the workingreticle 34, if the marks are used for alignment of the working reticle34, the relative positional error of the alignment marks 24A and 24B andthe pattern area 25 can be expected to be reduced. Alignment sensors 41Aand 41B for reticle alignment are arranged above the alignment marks 24Aand 24B. In this case as well, the fiducial marks 47A, 47B, thealignment marks 24A, 24B, and the alignment sensors 41A, 41B are usedfor alignment of the working reticle 34 with respect to the sample table43 (orthogonal coordinate system XY defined by two laserinterferometers).

Next, when performing overlay exposure, a not shown wafer alignmentsensor is used for alignment of the shot areas 48 on the wafer W. Next,the shot areas 48 on the wafer W to be exposed are successivelypositioned at the exposure position, then excimer laser light or otherexposure light IL1 is focused on the pattern area 25 of the workingreticle 34 by a not shown illumination system, whereby an image 27W ofthe master pattern 27 in the pattern area 25 reduced by a reduction rate1/β is exposed on the shot area 48. After the reduced image of themaster pattern 27 is exposed on each shot area of the wafer W by astep-and-repeat system in this way, the wafer W is developed, etched,and otherwise processed, whereby the circuit pattern of a layer of thesemiconductor device is formed in each shot area of the wafer W. Notethat it is also possible to use the step-and-scan method for scanexposure of each shot area of the wafer W.

According to the reticle exposure apparatus of the above embodiment ofthe present invention, by forming the first master identification marksM1 and second master identification marks M2 at the peripheral area 52around the pattern area 51 where the pattern Pi of the master reticle Riis formed, detecting the transfer position on the substrate 4 where thepattern of a master reticle Ri is to be formed by the first masteridentification marks M1, detecting the identification information foridentifying the master reticle Ri from another master reticle by thesecond master identification marks M2, and performing exposure based onthis information, if the operator (worker) of the reticle exposureapparatus specifies the master reticles required for the working reticleto be produced and sets them suitably in the reticle library 16, thereis no need to input other information etc., the number of work steps canbe greatly reduced, there are no longer input errors of informationetc., and the efficiency of production of a working reticle can begreatly improved.

Further, the first master identification marks M1 serve also as spatialimage measurement marks. If finding various correction values by spatialimage measurement of the first-master identification marks M1 orextracting the correction values stored in the reticle information andmaking corrections based on these, it is possible to improve thepositional accuracy or connection accuracy of the patterns and produce aphotomask (working reticle) 34 having a high accuracy master pattern.

Note that the present invention is not limited to the above embodiment.It is of course possible to use various configurations within a scopenot exceeding the gist of the present invention.

For example, in the above embodiment, a plurality of first masteridentification marks M1 were formed on the master reticle Ri, but thiswas done for spatial measurement at a plurality of locations on a masterreticle Ri to find correction values for various types of error, but thenumber may be one or a small number or a large number. Similarly, thesecond master identification mark M2 was made a single mark, but mayalso be a plurality of marks. Further, it is possible to form either ofthe first master identification mark M1 and second master identificationmark M2 or another master identification mark. For example, it ispossible to not set the transfer position information at the firstmaster identification marks M1, that is, make the first masteridentification marks M1 function only as spatial image measurement marksor not provide the first master identification marks M1 and storetransfer position information corresponding to the identificationinformation (ID number etc.) of the master reticle obtained by detectionof the second master identification marks in the above-mentioned storagedevice (exposure data file) 11 together with the reticle information.Further, the configurations of the first master identification marks M1and second master identification marks M2 are not limited to the above.In the above embodiment, the transfer position was identified by thepresence of mark elements 53X, 53Y at any of the four display areas RU,RD, LU, LD of the first master identification marks M1, but it is alsopossible to give meaning to the number of line-and-space patterns orpitch of arrangement etc. of the mark elements to set transfer positioninformation or other information. Further, to detect the first masteridentification marks M1 or second master identification marks M2, it ispossible to use the above-mentioned spatial-image measurement apparatusor alignment sensor or other apparatus for detecting items other thanthe master identification marks or to separately provide a detectionapparatus exclusively for the master identification marks.

Further, in the above embodiment, the second master identification markM2 was made a bar code mark set with identification information foridentification of one master reticle from another master reticle. Thereticle information corresponding to the identification information isstored in the storage device (exposure data file) 11, but it is possibleto set the reticle information in the second master identification markM2 itself. By doing this, it is possible to reduce the storage area ofthe storage device 11. The second master identification mark M2 is notlimited to a bar code. A matrix code, letters, symbols, or other codescan also be used. Further, in the above embodiment, the first masteridentification marks M1 formed on a master reticle Ri are made spatialimage measurement marks suited for measurement by the spatial imagemeasurement method, but they may also be diffraction grating marks. Notethat the exposure data file 11 storing the reticle information etc. maybe in the exposure apparatus itself (minicomputer etc.) or may be readfrom a host computer connected to a plurality of manufacturingfacilities (exposure apparatuses, coater developers, etc.)

Further, in the above embodiment, the master reticle Ri is aligned bymeasuring the alignment marks 21A and 21B, but it is also possible toalign it by using the first master identification marks M1 etc. By doingthis, it is no longer necessary to form marks just for alignment andtherefore the efficiency is higher. At this time, it is also possible todetect the master identification marks used also as the alignment marksnot by a spatial image measurement apparatus or bar code reader, butalso an alignment sensor. Further, the alignment sensor 23 for detectingthe marks on the substrate 4 is not limited to an off-axis type. It isalso possible to use a TTL (through-the-lens) type or a TTR(through-the-reticle) type. Further, it is possible to use not onlybroad band light, but also a single wavelength laser light ormultiwavelength light etc. Further, it is possible to use a system forphotoelectric detection of the diffracted light or scattered lightgenerated from the mark instead of the image processing system.

It is possible to employ various methods for correction of the imagingcharacteristics based on the above-mentioned reticle information orresults of the spatial image measurement. For example, it is alsopossible-to shift the position of the master reticle in the image fieldof the projection optical system 3, that is, the plane orthogonal to theoptical axis, or move the master reticle in a direction parallel to theoptical axis to tilt the master reticle with respect to the physicalplane of the projection optical system 3 (plane orthogonal to theoptical axis). Further, it is possible to enable movement of at leastone of the optical elements of the projection optical system 3 andadjust the optical performance of the projection optical system 3(imaging characteristics) or shift the center wavelength of the exposurelight IL slightly from the reference value. Further, it is possible tomake the image plane of the projection optical system 3 and thesubstrate 4 relatively move based on the output of a tilt_incidencelight type focus sensor for detecting the position of the substrate 4with respect to the optical axis direction (Z-direction) of theprojection optical system 3.

Further, it is also possible to correct the imaging characteristics by aplurality of master reticles used for the production of a workingreticle or correct the imaging characteristics by only a specific masterreticle. Further, it is possible to adjust for example the projectionmagnification for one or more master reticles among all of the masterreticles to correct the imaging characteristics and to for examplerotate the reticle for other master reticles to correct the imagingcharacteristics. Note that it is also possible to correct the imagingcharacteristics of the master reticles.

Further, when using an exposure apparatus (stepper) for keeping themaster reticle and the substrate substantially stationary andtransferring the pattern to the substrate (stepper), it is possible todivide the pattern of the master reticle into a plurality of sections bya reticle blind (field stop) arranged in the illumination system 1 andtransfer them to the substrate and to correct the imagingcharacteristics for each of the plurality of sections on the masterreticle.

Further, when transferring the pattern of a master reticle to thesubstrate 4 using the scan type exposure apparatus, the master reticleand the substrate are moved relatively with respect to the projectionoptical system 3. Therefore, in a scan type exposure apparatus, it ispossible to drive the reticle blind (field stop) arranged in theillumination system 1 and define the illumination region of the exposurelight on the master reticle to shift the position of the illuminationregion in the image field of the projection optical system 3. Further,it is possible to correct the imaging characteristics by slightlyshifting the scan direction of the master reticle and substrate forsynchronous movement or slightly rotating the master reticle forsynchronous movement in that state. Further, it is possible to correctthe imaging characteristics by moving at least one optical element inthe projection optical system 3. In addition, it is possible to correctthe imaging characteristics by shifting the scan speed from apredetermined speed ratio between the master reticle Ri and thesubstrate 4.

Further, since a plurality of master reticles Ri are successivelyexchanged to transfer master patterns Pi on the substrate 4, the timerequired for exposure of the substrate 4 becomes comparatively longerthan for exposure of the wafer W using the working reticle 34. Further,when the projection exposure apparatus of FIG. 2 uses an excimer laseras exposure light, a chemical amplification type resist is used for theresist 4. Therefore, sometimes the line width of the pattern image offor example the first master reticle R1 in the plurality of patternimages (resist pattern) formed on the substrate 4 does not become thetarget line width after the development. This is considered to arise dueto the difference in time from exposure until development (or baking)for each master reticle. Therefore, it is desirable to find the amountof change of line width for each master reticle by measurement orsimulation and finely adjust the amount of exposure of the substrate 4(resist) in accordance with the amount of change at the time of transferof the master pattern. Due to this, since the amount of exposure isadjusted for each master pattern, the change in line width of the resistpattern can be kept to a minimum.

The device pattern obtained by enlarging the device pattern formed onthe working reticle 34 may be divided into each of the element patterns,for example, divided into the dense patterns and isolated patterns, ordivided into each of the functional blocks to form master reticles so asto eliminate or reduce the stitched portions of the adjoining patternson the substrate 4. In this case, the master pattern of a single masterreticle is sometimes transferred to a plurality of areas on thesubstrate 4, so it is possible to reduce the number of the masterreticles used for the production of the working reticle. In this case,however, it is necessary to store and hold the correction values basedon the positions on the substrate 4 where the master patterns are to betransferred (for example, the correction values relating to the flexingaccompanying support of the substrate 4) in the reticle information.

Note that the “stitching” in the specification of the presentapplication means not only stitching of patterns, but also arrangementof one pattern and another pattern in a desired positional relationship.Regardless of the presence of the stitched portions of the patterns, theshot areas to which the patterns are transferred partially overlap withthe adjoining shot areas. That is, the overlay parts are exposedmultiple times.

Further, sometimes an identification code (bar code or 2-dimensionalcode etc.) including identification information (ID number etc.) isformed on the working reticle 34. In this case, it is desirable to forma pattern of the identification code enlarged by a on a master reticleRi the same as one of the plurality of master patterns Pi or a masterreticle exclusively for the identification code and transfer the reducedimage of the identification code on the substrate (blank) 4 togetherwith the plurality of master patterns using the reticle exposureapparatus of FIG. 2 by an electron beam lithography system, laser beamlithography system, optical type projection exposure apparatus, etc.Note that instead of using a reticle exposure apparatus (masterreticle), it is also possible to directly draw (form) the identificationcode on the substrate 4 using an electron beam lithography system orlaser beam lithography system etc. Similarly, it is possible to formalignment marks or spatial measurement marks or information other thanthese (letters etc.) on the working reticle 34.

Further, when successively transferring a plurality of master patternsPi on the substrate 4, the substrate sometimes deforms due to heat dueto the irradiation of the exposure light IL. Therefore, when the amountof deformation occurring due to irradiation by exposure light cannot beignored, it is preferable to find the amount of deformation by actualmeasurement or calculation (simulation) to determine the abovecorrection values a to f.

In the above embodiments, the exposure apparatus shown in FIG. 5 wasexplained as one used for production of a semiconductor device, but itmay also be an exposure apparatus etc. used for the production of adisplay device including liquid crystal display or plasma display, athin film magnetic head, a pickup element (CCD), a vibrator used in acellular phone or home game system, etc.

In the exposure apparatus of FIG. 5, the projection optical system 42was a reduction system, but the projection optical system 42 may also bean equal magnification system or an enlargement system. Further, theprojection optical system 42 may be any of a dioptric system comprisedof only a plurality of refraction elements, a catoptric system comprisedof only a plurality of reflection elements, and a catadioptric systemcomprised of refraction elements and reflection elements. Further, theexposure apparatus of FIG. 5 may be of the proximity type or a contacttype not using a projection optical system or a stationary exposure typeand scan exposure type.

Further, the exposure apparatus of FIG. 5 is not limited to astep-and-repeat system or step-and-scan system and may also be astep-and-stitch system which partially overlays a plurality of shotareas on a substrate 4 to transfer one pattern on the plurality of shotareas. Further, the exposure apparatus of FIG. 5 may also be a mirrorprojection system forming a plurality of patterns on the entire surfaceof the photosensitive substrate by a single scan exposure. Note that inthe step-and-stitch system, when transferring a pattern to the shotareas, either of the stationary exposure system or the scan exposuresystem may be used. The scan exposure system is disclosed in for exampleJapanese Unexamined Patent Publication (Kokai) No. 4-196513 and itscorresponding U.S. Pat. No. 5,473,410. The disclosure of thispublication and the U.S. patent are incorporated by reference and madepart of the disclosure of this description in so far as allowed by thedomestic laws of the designated countries or elected countriesdesignated or elected in this international application.

Further, in the exposure apparatus of FIG. 5, it is possible to use asthe exposure use illumination light, g-rays (wavelength 436 nm) ori-rays (wavelength 365 nm) emitted from a mercury lamp or a higherharmonic of a KrF excimer laser (wavelength 248 nm), an ArF excimerlaser (wavelength 193 nm), an F₂ laser (wavelength 157 nm), an Ar₂laser, and metal vapor laser or YAG laser. Further, it is also possibleto amplify an infrared region or visible region single wavelength laserlight emitted from a DFB semiconductor laser or fiber laser by forexample an erbium (or both erbium and yttrium) doped fiber amplifier anduse the harmonic obtained by converting the wavelength to ultravioletlight using a nonlinear optical crystal (details explained later).Further, the exposure use illumination light is not limited to the abovefar ultraviolet band or vacuum ultraviolet band (wavelength 120 to 200nm) and may also be a soft X-ray region generated from a laser plasmalight source or SOR (wavelength of about 5 to 50 nm), for example, EUV(extreme ultraviolet) light of a wavelength of 13.4 nm or 11.5 nm orsoft X-ray region (wavelength not more than 1 nm). Note that in an EUVexposure apparatus, a reflection type reticle (mask) is used. Also, theprojection optical system is a catoptric system which is a reductionsystem telecentric at only the imaging plane side and is comprised of aplurality of (3 to 6) reflection optical elements.

Further, the present invention may also be applied to a device exposureapparatus using an electron beam, ion beam, or other charged particlebeam. Note that an electron beam exposure apparatus may be of the directdrawing type (for example, including a cell projection system, variablyshaped beam system, aperture array system, etc.) or a projection system(for example a system exposure an area of about 250 nm square on aphotosensitive substrate at one time using a transmission type mask). Inthe direct drawing system, no mask is used, but it is also possible touse an exposure apparatus according to the present invention to producea cell, aperture, etc. used for shaping an electron beam.

In this way, the exposure apparatus of FIG. 5 may be of anyconfiguration or system so long as using a mask or reticle (includingcell or aperture). On the other hand, the exposure apparatus forproduction of a mask or reticle (FIG. 2 to FIG. 4) may be anyconfiguration or system similar to that of the above-mentioned exposureapparatus for production of a device (FIG. 5), but consideringproduction of a master mask (master reticle) etc., is preferably aprojection type, in particular a reduction projection type. Note that inthe exposure apparatus shown in FIG. 2 to FIG. 4, the substrate 4 wasfixed on the sample table 5, but to avoid deformation of the substrate 4due to vacuum chucking or electrostatic chucking etc., it is desirableto support the substrate 4 at a plurality of points (for example threepoints) without chucking on the sample table 5.

In the above embodiments, however, use was made of a transparentsubstrate (silica glass etc.) as the substrate (blank) 4. This isbecause it is predicated on the exposure illumination light IL1 used inthe exposure apparatus (FIG. 5) to which the substrate 4, that is, theworking reticle 34, is applied being the vacuum ultraviolet band(wavelength df about 100 to 200 nm) or a wavelength band longer thanthat. Here, when the wavelength band of the exposure illumination lightIL1 is at least about 190 nm, it is possible to use silica glass as thesubstrate 4, but with a wavelength shorter than that, in particular awavelength of 100 to 180 nm, it becomes difficult to use silica glass asthe substrate 4 in regard to the transmittance. Therefore, when thewavelength of the exposure illumination light IL1 is 100 to 180 nm, itis preferable to use for example fluorite, fluorine-doped silica glass,rock crystal, LiF, LaF₃, lithium-calcium-aluminum fluoride (LiCaAlFcrystal), etc. as the substrate 4. Note that the mask material formed onthe substrate 4 may be suitably selected in accordance with the type ofthe working reticle 34 and is not limited to the above-mentioned chromeetc.

In the above EUV exposure apparatus, a reflection type mask is used. Amultilayer film comprised of several dozen alternately coated layers ofsilicon and molybdenum when the exposure wavelength is 13.4 nm or amultilayer film comprised of several dozen alternately coated layers ofmolybdenum and beryllium when the exposure wavelength is 11.5 nm isformed on the surface of the substrate 4. It is possible to use not onlya glass substrate, but also a silicon wafer etc. as the substrate 4. Ina proximity type X-ray exposure apparatus or electron beam or ion beamor other charged particle beam exposure apparatus etc., a transmissiontype mask (stencil mask, membrane mask) is used, so a silicon wafer etc.is used as the substrate 4.

The exposure apparatus of the present embodiment shown in each of FIG. 2and FIG. 5 may be produced by affixing at least part of a projectionoptical system comprised of a plurality of optical elements assembled ina mirror barrel and an illumination system comprised of a plurality ofoptical elements (including optical integrator etc.) to a framesupported by a plurality of anti-vibration pads and optically adjustingthe illumination system and the projection optical system and byconnecting wiring and piping to the reticle stage (2) or wafer stage(sample table 5 and XY stage 6) comprised of the large number ofmechanical parts and drive system (linear motor etc.), etc., arrangingthe fiducial mark member (12 or 46), photoelectric sensor (56), etc. tothe wafer stage, and performing overall adjustment (electricaladjustment, confirmation of operation, etc.) Note that the exposureapparatus is desirably manufactured in a clean room controlled intemperature and cleanness etc.

The semiconductor device is produced through a step of design of thefunctions and performance of the device, a step of production of aworking reticle by the exposure apparatus of FIG. 2 using the abovemaster reticle based on the design step, a step of production of a waferfrom a silicon material, a step of transferring a pattern of the workingreticle on to a wafer using an exposure apparatus of FIG. 5, a step ofassembly of the device (including dicing, bonding, packaging, etc.), andan inspection step.

As the light source, it is possible to use various ones other than thoseillustrated. For example, it is possible to use an infrared region orvisible region single wavelength laser light emitted from a DFBsemiconductor laser or fiber laser amplified by for example an erbium(or both erbium and yttrium) doped fiber amplifier and use the harmonicobtained by converting the wavelength to ultraviolet light using anonlinear optical crystal.

For example, if the oscillation wavelength of the single wavelengthlaser is made a range of 1.51 to 1.59 μm, an 8th harmonic of anoscillation wavelength in the range of 189 to 199 nm or a 10th harmonicof an oscillation wavelength in the range of 151 to 159 nm is output. Inparticular, if the oscillation wavelength is made one in the range of1.544 to 1.553 μm, ultraviolet light of an 8th harmonic in the range of193 to 194 nm, that is, a wavelength substantially the same as that ofan ArF excimer laser, is obtained. If the oscillation wavelength is madeone in the range of 1.57 to 1.58 μm, ultraviolet light of a 10thharmonic in the range of 157 to 158 nm, that is, a wavelengthsubstantially the same as that of an F₂ laser, is obtained.

Further, if the oscillation wavelength is made one in the range of 1.03to 1.12 μm, a 7th harmonic of an oscillation wavelength in the range of147 to 160 nm is output. In particular, if the oscillation wavelength ismade one in the range of 1.099 to 1.106 μm, ultraviolet light of a 7thharmonic in the range of 157 to 158 nm, that is, a wavelengthsubstantially the same as that of an F₂ laser, is obtained. Note that asthe single wavelength oscillation laser, a yttrium-doped fiber laser isused.

All of the disclosure of Japanese Patent Application No. 10-316129,filed on Nov. 6, 1998, including the specification, claims, drawings,and abstract, are incorporated herein by reference in its entirety.

What is claimed is:
 1. A method of performing stitching exposure on aplurality of regions on different positions on a substrate, comprisingthe steps of: detecting an identification pattern formed on a maskhaving a pattern to be transferred to at least one of the plurality ofregions, including information on the at least one region; and exposingthe at least one region based on the information on the at least oneregion obtained by the detection of the identification pattern so as totransfer the mask pattern to the at least one region via a projectionoptical system.
 2. A method according to claim 1, wherein theidentification pattern includes information on the mask besides theinformation on the at least one region.
 3. A method according to claim2, wherein the identification pattern has a first pattern including theinformation on the at least one region and a second pattern which isdifferent from the first pattern including the information on the mask.4. A method according to claim 3, wherein the second pattern is abar-code mark.
 5. A method according to claim 2, wherein the informationon the mask includes at least one of correction information used foralignment of a pattern image of the mask and the substrate andinformation on an exposure condition for the at least one region.
 6. Amethod according to claim 1, wherein the identification pattern includescorrection information for canceling at least one of deformation of themask, aberration of the projection optical system and deformation of thesubstrate.
 7. A method according to claim 1, wherein the identificationpattern includes information on an exposure condition for the at leastone region.
 8. A method according to claim 1, wherein the identificationpattern is detected in a state where the mask is held on a mask stage.9. A method according to claim 1, wherein the identification patternincludes at least a bar-code mark.
 10. A method according to claim 1,wherein the identification pattern includes a measurement mark by whicha projection image is detected at least on an image plane side of theprojection optical system.
 11. A method according to claim 10, whereinalignment of the mask is carried out by using the identificationpattern.
 12. A method according to claim 1, wherein a part of anenlarged pattern of a device pattern to be formed on the plurality ofregions by the stitching exposure is respectively formed on a pluralityof masks including the mask, and the plurality of masks have anidentification pattern including information on a specified region onwhich a part of the enlarged pattern is transferred among the pluralityof regions; and a reduced image of the part of the enlarged pattern istransferred to the specified region via the projection optical systembased on the information on the specified region obtained by thedetection of the identification pattern for each of the masks.
 13. Amethod according to claim 1, wherein during the stitching exposure, apart of the plurality of regions has a different exposure amount.
 14. Amethod according to claim 13, wherein an exposure amount on theplurality of regions is respectively determined in accordance with achange amount of a line width of a pattern image to be transferred. 15.A process of producing a photomask comprising producing a photomaskhaving a device pattern using a method of exposure as set forth inclaim
 1. 16. A photomask produced using a method of exposure as setforth in claim
 1. 17. A process of producing a device using a photomaskas set forth in claim
 16. 18. An exposure apparatus for performingstitching exposure on a plurality of regions of different positions on asubstrate via a projection optical system, comprising: a holding unitwhich holds at respectively different positions a plurality of masksincluding a mask having a pattern to be transferred to at least one ofthe plurality of regions and an identification pattern includinginformation on the at least one region; a mask stage arranged on anobject plane side of the projection optical system; a transfer unitwhich respectively transfers the plurality of masks between the holdingunit and the mask stage; a substrate stage arranged on an image planeside of the projection optical system; a detection device which performsdetection by illuminating the identification pattern of the mask; and acontrol unit connected to the detection device, which controls exposureof the at least one region based on the information on the at least oneregion obtained by the detection of the identification pattern so as totransfer the mask pattern to the at least one region via the projectionoptical system.
 19. An apparatus according to claim 18, wherein theidentification pattern includes information on the mask besides theinformation on the at least one region.
 20. An apparatus according toclaim 19, wherein the information on the mask includes at least one ofcorrection information used for alignment of a pattern image of the maskand the substrate and information on an exposure condition for the atleast one region.
 21. An apparatus according to claim 18, wherein theplurality of masks respectively have a part of an enlarged pattern of adevice pattern to be formed on the plurality of regions by the stitchingexposure and an identification pattern including information on aspecified region on which a part of the enlarged pattern is transferredamong the plurality of regions; and a reduced image of the part of theenlarged pattern is transferred on the specified region via theprojection optical system based on the information on the specifiedregion obtained by the detection of the identification pattern for eachof the masks.
 22. An apparatus according to claim 18, wherein during thestitching exposure, a part of the plurality of regions has a differentexposure amount.
 23. An apparatus according to claim 22, wherein anexposure amount on the plurality of regions is respectively determinedin accordance with a change amount of a line width of a pattern image tobe transferred.
 24. A process of producing a photomask comprisingproducing a photomask having a device pattern using an exposureapparatus as set forth in claim
 18. 25. A photomask produced using anexposure apparatus as set A forth in claim 18.